Intelligence transmission



Aug. 1o, 1937.

A V. BEDFORD INTELLIGENCE TRANSMISSION Filed April 8, 1933 4 Sheets-Sheet l Aug. .10, 1937. A. v. BEDFORD 2,089,639

INTELLIGENCE TRANSMISSION Filed April 8, 1953 4 Sheets-Shet 5 I I I l l I I I I I I Dil/1 V50 SWIM/0 MWf I l I I l ATTORNEY Aug., 1o, 19,37.v

` A. v. BEDFORD INTELLIGENCE TRANSMISSION Filed April 8, 1935 izq, 6'

4 Sheets-Sheet 4 we@ M ATTO RN EY Patented Aug. 10, 1937 PATENT oFFIcE 2,089,639 INTELLIGENCE TRANSMISSION Alda V. Bedford, Collingswood, N. J., assigner to Radio Corporation of America, a corporation oi' Delaware Application April 8, 1933. Serial No. 665,072

16 Claims.

'Ihe present invention relates broadly to television systems and it is directed particularly to television systems wherein the pictorial action is viewed simultaneously with the production of audible effects which are coordinated with the visual action taking place at the transmitter point.

It has, in general, been found in connectionv with any type of image viewing system, whether it be motion pictures or television, that the action portrayed in the Vform of a light, electrooptical or 'other type of image is made considerably more realistic if the visible indications are accompanied by audible indications. It is with the thought in mind that the efilciency, commerical utility, and interest in the system is con- I transmission of these intelligence signals. Such a system would, however, require and demand considerably greater space in the ether than a system ofthe type which is here being proposed.

Further, systems of the type wherein two dis.- tinct frequency bands, and, therefore two separate transmitters, are needed are not, of course, emcient since they require not only separate amplifying systems for the sound Vand picture signals but also require separately generated car,- rier frequencies and independent means for modulating these separate carrier frequencies. In addition, there is a great loss of available'time 40 for transmitting the signals and especially the picture signals on apparatus of this type because where ay cathode ray device or other type of electronic device is used as either the image transmitting instrumentality or as the image reproducing or reconstructing device, provision should be made for the so-called uni-lateral scanning. By uni-lateral scanning is meant .scanning action taking place always in one direction, that is, for example, always from left to right on a viewing area. So arranged, it is quite obvious that in a system using a cathode ray tube as the image reconstructing device, for

' example, so that an electron pencil causes the electro-optical eiects, the electron pencil must move, for example, from left to right at a relatively slow rate, or from right to left, that is, the return line, at a relatively faster rate. in order that the loss in time of actual intelligence transmission be reduced to a minimum.

According to one suitable form of transmission 5 these rates may be of any order from six to one to ten to one, for example. One suitable ratio of the ray motion in the two directions is such that the slow motion period of ray traversal occupies relatively of the complete scanning 10 cycle necessary to produce one complete elemental strip or line of the constructed image' subject, and then the rapid motion of the ray in the reverse direction occurs within a 10% perio`d of the scanning cycle. 15-

- If now the ratio of nine to one, above suggested, is to be maintained, it can be seen that during the return line period of 10% there is really no useful transmission being carried out. If it is further assumed that the frequency band necessary to transmit a picture of the desired detail is, say, somewhat in excess of one megacycle which, for example, would be required that the subject divided for scanning and analyzing purposes into slightly more than 300 distinct 25- lines or elemental strips, and each elemental strip or line comprising 300 or more independent and ,distinct elemental areas where the repetition frequency is twenty-four complete image reproductions per second. 30

According to the above suggested conditions, only 1% of the selected frequency band can be utilized to produce an electro-optical image effect with the above suggested detail. If thesubject is assumed to be divided into 300 distinct 35 elemental strips or lines and 24 complete im-A ages' per second are being transmitted it is apparent that the intelligence representing each elemental strip must be transmitted during ths of 1/7200ths of a second and that during the 40 remaining 1/72,000ths second there will be no useful image transmission, the result is that there is a loss of somewhat in excess of 100,000 cycles in the frequency band for this type of transmission. Of course, such a loss means that the load upon 45 the transmitter does not remain constant or substantially constant and that a considerable portion of the available frequency band cannot, in effect, bel utilized.

It is one of the objects of this invention to 50 provide ways and means by which this period of what might be termed lost energy transmission may be utilized. It is, therefore, proposed to transmit on the television carrier frequency during the time intervals between the successive 55 transmission of intelligence effects representing the values of light and shadow for each elemental strip of the scanned subject, additional signals to represent the soundwhich occurred during .the transmission of the image signals representing the elemental strip just previously scanned. According to this form of the invention, the load on the transmitter will for ths of the time be a load determined by the image signals and during the remaining 116th of the time, disregarding for the time being synchronizing signals, a load d ue to sound signals accompanying the image signals. Y

It has already been `proposed in transmitting television image Asignals to follow the image signals representative of each elemental strip of the subject by one or more synchronizing impulses. At the various points of reception of the transmitted image these auxiliary signalsl serve to synchronizeand coordinate in space relationship the reproduced electrooptical effects representative of the subject located at the point .of transmission. In this way a portionvoi the time loss due to the reversal of the scanning path has been compensated but, nevertheless, the time required to transmit the synchronizing signals is only relatively short compared to the total return line period or, in other words, the time required for the cathode ray pencil to return to its' original starting position.

In the preferred forms of cathode ray television apparatus now in use the position control of the .cathode ray pencil is provided by suitably arranged deecting circuitsoperating under the control of energy having a wave formation which changes along a saw-tooth path. Such a wave formation can be produced through the use of relaxation oscillators, .dynatr'on oscillators, gridcontrolled oscillators For the like so that the output voltage or current varies according to. a saw-tooth pattern, by which is meant that there is a change in the intensity of the output energy serving as the control current or the controlling voltage for the tubev ray deiiection system from minimum to maximum in one direction at a very `slow rate, and in the .other direction at a very y rapid rate or viceversa. According to the above suggested arrangement the slow-change period will occupy fths of the scanning cycle for one line or elemental strip of the subject and the rapidly changing portion will` occupy the remaining 116th of the scanning cycle for each elemental strip. y

Suppose now that the line scanning frequency is of the, order of 4,800 to approximately 8,000 cycles per second, which, for example,4 would occur where the subject is divided into a number oi' elemental strips varying between 200 and 330.

It can be seen that this frequency is not quite suicient for proper sound modulation impulses because thelimpulse carrier is not suilici'ent for high quality. However, two or three times the .line frequency would be satisfactory because subject, certain portionsof the sound occurring and then also to select a certain portion of the sound actualy occurring during the so-called return line period. It, now,l it is possible to select during the picture scanning period one distinct portion or slice of sound and another distinct portion or slice during the return line period, and ii' it is possible to delay the sound first selected during the picture scanning period until a time period just immediately prior to the time period of actual occurrence of sound selected.

during the return line period, it can-be seen that these two sounds can 'then be transmitted to follow the picture and synchronizing signal indications. These sound signals then can be caused to control or modulate the television transmitter during the return lineperiod.

To 'provide for operating this arrangement, it is necessary then to arrange at the receiving end of the system a suitable means by which the sound signals actuallyoccurring during the return line period are delayed in reproduction by a time period corresponding to the delay period at which the sound originating at the point o f transmission during the picture scanning period is transmitted. The proper relationship between both sounds will then be -maintained except that both sounds have been delayed in time relationship by xed and equal amounts. From such an arrangement it can be seen that by selecting asfew as two distinct slices or portions of sound the sound signals selected will each have an amplitude corresponding to the amplitude of the sound actually present. By plotting graphically these independent sound signals the resulting curve obtained' by the diierences in the sound signals from zero intensity will be an envelope corresponding exactly to the sound actually present in the lrst instance. Thus, it has been proven and established .that to reproduce sound it is not necessary that all of the sound actually existent should be transmitted but only just sufficient sound to provide enough points of plotting in order that the sound envelope may be determined. This relationship may be, for example, as little as 5% of the sound actually existing and due to the fact that a suitable filter in the receiver so smooths out the sound by the points represented so that there is reconstructed the envelope of thev various points of varying amplitude and the reproduced sounds will be, so far as the listener is concerned, exactly the same as ii all of the originally produced sound were actually present.

Therefore, it is one of the objects of my invention to provide waysvand means by which it is possible to transmit on a single carrier'frequency,

signals representing picture shade values, syn. chronizlng impulses and sound indications.

Another object of the invention is -.to provide.v

ways and means by which a substantialperiod' of the time available may be used for transmitting picture signals and in which a small portion of the time period available may be Vutilized for transmitting synchronizing and sound signals.

Another object of the invention is to provide ways and means by which picture signals may be transmitted in their entirety and sound signals which are later to be reconstructed into the total sound available may be transmitted in minute proportions to the total sound signals available.

Still afurther object of the invention is' to provide ways and means by which certain predetermined differential sections or portions or slices of the total soundenergy available may be selected and used to control the transmitter.

energy may be further identified as including a differential segment of the area beneath the curve representing the envelope of the total sound available. In other words, what is really transmitted may be considered as ai' derivative of the band frequency wherein by the term derivative is meant index portion, a derived curve or any other form of signal which is derived from and whose value is determined by the characteristics of the original frequency. 0f course, it will be apparent in this connection also that the original sound frequencies can be passed through any desired type of distorting device to produce and provide suitable other forms of derivatives. Such devices may be, for example, frequency multipliers and the like.

Other objects andA advantages of the invention are'to provide ways and means by which a plurality of different types of signals may be transmitted from a single transmitter over any appropriate connecting channel, such as a wire line or radio channel, to points of. reception and provide at the receiving points the eect of continuity of both forms of message signals at the various points of reception irrespective of the actual interruption of each type of transmission for predetermined time periods at the point of transmission.

Other and further objectsof the invention are, of course, to provide a system for transmitting sound and image signals wherein use is made -of o the time interval between successive scanning lines, assuming the system to be applied specifically to television apparatus, to receive and store up the essential information which in the receiving device is effectively released after certain fixed delay periods and then used to reconstruct the signal which the transmitted information contained. In this connection it may be noted that the period within which the transmission of picture signals is described could be used, where depicture signals so that this system as dened by the present disclosure could be used as a means for transmitting multiple sound signals of dif ferent subject matter over al single radio or other communication channel.

Other objects of the invention are to provide a l system for combined visual and audible signals which is relatively simple in its construction and 60 arrangement of parts; easy to` operate; capable 70 following specification and claims in connection with the accompanying drawings illustrating one preferred form of my invention, wherein:

Fig. 1 illustrates conventionally and in block diagram formation suitable arrangements for 75 transmitting and receiving apparatus;

sired, to contain other sound signals instead of Fig. 2 illustrates a portion of the transmitter end of the system;

Fig. 3 illustrates the relationship between picture, synchronizing and sound signals so far as time separation and division is concerned;

Fig. 4 illustrates conventionally various curves designated as a through i inclusive to show and illustrate various control or signal wave formations at the transmitter;

Fig. 5 illustrates diagrammatically one form of receiver apparatus; and

Fig. 6 illustrates by curves d through r inclusive diagrammatically the wave formations existing in the receiver inl contrast to the -wave forms found at the transmitter.

If reference is now made to the accompanying drawings for an understanding of the operation of this invention it may b e assumed that television transmission is carried on according to well known and established principles of operation. For example, the television transmission may be carried out in accordance with the prior teachings of V. K. Zworykin as expressed, for example, in copending application Serial No. 574,772, filed November 13, 1931, assigned to Radio Corporation of America` except that no reference need be made to a particular color system and the application referred to is mentioned solely because of the fact that it illustrates one suitable form of cathode ray image scanning device. It is also to be understood that any form of mechanical scanning system may be used for producing the image signais provided that there is provided between the production of the series of the electrical signais representing successive lines or elemental strips of the subject of which the image is being produced a slight time separation of the order of Meth or less of the scanning time period required to transmit a single elemental strip or line of the subject.

If, for example, it is assumed that the subject being analyzed is scanned over its entire area at a repetition rate of 24 cycles per second, this being the customary film speed of standard motion picture lm, and if it is assumed that each lm frame is divided into a sufilciont number of elemental strips that the product ofthe individual elemental strips and the image scanning rate per second is of the order of approximately 7000, it can be seen that the entire time required to scan each elemental strip of the subject will be of the order oi' 1/7000th of a second. Since all of this 1/7000th of a second time period cannot actually be used to transmit signal indications representative of light and shadow on each successive elemental area in a television system involving the use of cathode ray devices for scanning or reproducing the image, for example, due to the fact that wherever a cathode ray tube is used as the image scanning and/or reconstructing device time must be allowed for the return line" period of the ray. The actual time allowed for the transmission o'f image signals per scanning cycle is of the order of 1/8000th of a second with the diiference between the rate of the scanning cycle 1/7000th oi' a second) and the time used for actual transmission being provided for the so-called return line period.

So arranged, the television scanning device i is operated to test or analyze the varying intensities of light and shadow on each elemental area. of a subject. VIf it is assumed that the device -I is a cathode ray.tube of the general type disclosed by Zworykin and others this tube may operate under the control of the horizontal synchronizing signal source 3 and the vertical synchronizing or framing signal source 5 each of which preferably generates a saw-toothwave form output and which is adapted to control the deecting elds serving to control the motion or deflection of the cathode pencil within the television scanning device l. So arranged, the horizontal frequency may have a frequency of the'order of 7000 cycles and the vertical synchronizing :frequency may have a frequency of the order of 24 cycles per second.

Each of these sources 3 and 5 serves to control and bias to cut-ofi. at predeterminedtimes the television signal amplier 'I which has its input circuit supplied with energy from the television scanner l so that when the amplifier is operative the signals produced from the television scanner are suitably amplified but at other times there will be no output from the amplifier. By this arrangement the television amplifier is so arranged that during the return line or rapidly changing period of the saw-tooth cycle the out-` put is negative.

The output energy from the television ampli.

' 3 and the vertical synchronizing source 5, which signals have previously been amplified by means of the amplifier Hl so that they are 180 out of phase with respect to the picture signals. Where desired, the energy following each series of signals representative of the variations in light and shadow and serving to represent the synchronizing signals may be produced by the scanning element itself as disclosed, for example, by copending application of A. W. Vance, Serial No. 544,959, filed June 17, 1931, assigned to Radio Corporation of America. v

AThe speech or laudible signals which accom- I pany the pictorial representations transmitted by the television scanner i are caused to influence the sound signal'transmitter Il and are then supplied to the sound amplifier I3 whose output energy is directed through a sound delay unit l5 of which the purpose will hereinafter be explained. The output from the sound delay unit lI5 is then supplied to a sound amplifier device Il to which in turn is supplied energy from a correetingimpulse source I 9 of which the purpose will also hereinafter be explained. The sound signals thus selected are then caused to be passed to the combined signal amplifier 9 to which it has been explained above the picture and synchronizing signals are supplied.

The output energy from the combined signal amplier representing sound, picture and synchronizing signals is directed to the modulator 2| to which energy from the carrier frequency oscillator 23 is supplied and the modulated carrier frequency is suitably amplified by the amplifier 25 and transmitted by way of the connecting channel 2l herein indicated as a radio channel, although a wire connecting link is equally suitable, to a receiving point where this energy is amplified and detected in well known manner by the receiving amplifier and detector 29.

As the received energy includes sound, synchronizing and picture signals, it is desirable that these signals be appropriately separated one from' These separated signals representing the picture and the synchronizing impulses are supplied to the picture signal amplifier 35 and to the vertical and horizontal synchronizing control devices 3| and 33, respectively.

As is now well known in the art, vertical synchronizing signals which may be appropriately controlled from the transmitted signals cause the scanning cycle to be repeated at a rate of 24 complete image representations per second, for example, and are effective for control during the time interval between the completion of scanning of the last or lowermost elemental strip of the subject, for example, and the start or uppermost elemental strip of the next succeeding elemental strip of the subject. The vertical synchronizing signal is adapted not only to control the position at which the electro-optical effects in the image reconstructing device 31 are produced, but also serves to render the picture signal amplifier or the image reconstructing device, or both, as desired, inoperative during this so-called return line period. Similarly, the horizontal synchronizing system which controls the line scanning rate is adapted to render either the picture signal amplifier or the image reconstructing device inoperative during the return line period between the reproduction of successive elemental strips. This type of control is well known and does not constitute a part of the present invention except insofar as it cooperates with the general combination of the various other elements to include new and novel subject matter.

In order to receive and reproduce the sound signals special arrangements must be made in the receiver. These features will b e described later in this disclosure after making further description of the transmitter end of the system. If reference is now made to Fig. 3 illustrating the relationship between the instantaneous position of the cathode ray pencil and the time, it can be seen that during the time period TI the deflection of the ray is increasing from a minimum to a maximum and during the time period T2 the cathode ray pencil is being returned from a position of maximum deflection to a. position of minimum deflection, during which period this band required for transmission is of the order of 1 mega-cycle, then during the period T2 there is transmitted substantially 100 kc. of energy which normally would not be put to any useful purpose. during the time period T2 the representations of the sound accompanying the picture action which is to be portrayed as occurring within the time period TI.

According to the present suggested scheme it is proposed to select during the time period TI an elemental strip or segment'ofV sound, generally designated as a, which occurs substantially midway between the positions of zero and maximum deflection and to select a second elemental segment or strip during the time period T2, which has been designated as b. However, it is impossible to transmit the sound signal a at the point in time where it is actually produced since it is at this time that the picture signals are being transmitted. Therefore, in order to bring the sound signal represented by the strip a within the idle period of the transmitter this sound signal Therefore, itV is proposed to transmit position of maximum deection 'of the cathodeA ray pencil of the scanning device.' designated as time period B, and the time at which the sound signal a' is to be transmitted, as shown by Fig. 3 for example. According to the system shown by Fig. 2 there is shown an arrangement which is intended to combine substantially the sound delay circuit, the sound amplier, and the impulse signal source, designated as I5, I1 and i9 respectively by Fig. 1, and to supply the resulting output signals to the combined signal amplifier 9 of Fig. 1. The amplified signals from the sound signal amplifier i3 are impressed upon the terminal 4| while suitable impulse signals from the source I9 are supplied to the terminal 49. The

impulse signals may be generated by any desired from a light source is directed to a photoelectric tube and amplifier, where the disk rotates at a speed commensurate with the frequency of the impulse desired, or the signals may be produced and generated by any other suitable form of arrangement. This impulse source is, of course,

40 synchronous with the picture scanner deecting circuits.

According to the present invention this correcting impulse signal in the form of a synchronizing impulse, as shown by Fig. 4a, which has a frequency of the order of 7000 cycles and is preferably an impulse wave of the general form indicated. It is to be assumed for the purpose of understanding this invention that this signal is so timed that one impulse occurs at the vend of each scanning line of the'picture, that is, after each scanning period A B (see Fig. 3). The impulse so produced is applied to the terminal point 43 and is then passed along the artificial line or impulse delay network 45 comprisinga plurality of series inductance and shunt capacity elements 41 and 49. This artificial' line acts to delay the impulse so that the wave at the top of the delay line reaching the point 50 is delayed .05TI seconds. where TI equals 1/7000th of a second as has been shown by the curve illustrated in Fig. 4b. This delayed impulse will, for convenience of description, herein be termed the odd impulse. The wave appearing across the terminating resistance 5| of this artificial line 45 is the result of the synchronizing impulse of Fig. 4a being delayed an. additional .05TI seconds. This impulse may, for example, be termed for convenience of reference the even impulse, and is shown in Fig. 4c.

The wave form illustrated for example by curve d of Fig. 4 is a part of the sound wave applied from the sound amplifier i3 to the input terminal 4I of the sound delay unit i5. A part of this sound energy is impressed by Way of a conductor and suitable coupling capacity 53 upon the screen electrode 51 of the screen grid tube 55. This tube 55 is normally biased to cut-off by its control grid 59 and passes no plate current except at time periods when the even impulses arrive from the artificial line 45 and are applied to the control electrode 59 of the screen grid tube 55 by way oi' a capacity 6| connected with the end of the articial line 45. The amplitude of the impulses of current that flow is proportional to the instantaneous sound wave voltage and hence the voltage across the output resistor 53 during the time period a and .b of the time period T2 (see Fig. 3) is representative of a sound signal and are negative. These modulated impulses are shown by Fig., 4e with the polarity changed to positive and altered scale to show how the height of the impulses is controlled by the sound wave applied to the input terminal.

In a similar manner the odd" impulses of the curve bof Fig. 4 are supplied to the tube 65 and are controlled by the delayed sound wave signals (shown by Fig. 4f) which are also applied to the tube 65. These delayed sound wave impulses appear across the terminating resistor 51 of the delay line 69 formed from a combination of series inductance and shunt capacity elements 1l and 13 which terminates at the resistor 61. 'I'he delay network 69 has a time delay period equal to approximately 0.5TI.

'Ihe modulated impulses resulting from the 'delayed sound signals are shown graphically by Fig. 4g. It should be noted particularly in this connection that the delayed sound wave appearingV across the resistor 61 at the end of the artificial line 69, winch signal modulates the odd impulse from the artificial or delay line 45, is really that part of the sound which originally occurs rst in time and hence must be made to reach the loudspeaker or sound reproducer first as regards time in the final receiver. 'Ihe time delay in the articial line 69 is substantially equal to one-half the time period TI so that the odd impulses are modulated by the portions of the sound belonging midway between the parts modulating the even impulses.

The grid of the tube 15 is excited by the simple undelayed synchronizing impulses shown by the curve 4a without modulating. VThe grid of the tube 11 is excited by the picture signal originating from the picture signal amplier 1, which is such a curve as the dotted line curve shown by Fig. 4i, which is arranged to have a fixed value approximately zero during the -time of the three impulses included as a part of the curve 4h to indicate synchronizing signals and speech or sound signals. The plate resistor 63 above mentioned may be common for all tubes 15, 65, 51 and 11 and hence serves to combine the waves shown by Figs. 4a, 4e, 4g and 4i, as shown. The amplified output energy from the combined signal amplifier 9 will then be a signal which contains the information for reconstructing both picture and sound, as can be seen more clearly from Fig. 67', and this signal together with the included synchronizing impulse is then transmitted by a single radio channel.

- At the receiver end of the system signals may be received in any desired and preferred manner. For example, the type of receiver may be, in the broadest sense, of the general form suggested and disclosed by copending application of J. Weinberg, T. A. Smith and G. Rodman, Serial No. 360,065, flied May 3, 1929 or in accordance with the disclosure of copending application of W. L. Carlson, serial No. 583,193, med December 26, 1931 which applications are assigned to Radio Corporation of America. So arranged, the signais received are conventionally shown as being separated in and by the receiving amplifier 29 and then'supplied to the vertical synchronizing signal control device, the horizontal synchronizing signal control device and the picture signal amplifier 3|, 33 and 35, respectively. The sound signals and one of the synchronizing impulses (also the picture signal) are then arranged so as to be supplied to the synchronizing impulse selector 1i, the even impulse selector 13 and the odd impulse selector 15, each of which arrangements is more particularly shown in its preferred form by Fig. 5 of the accompanying drawings.

If reference is now made to Fig. 5 a portion of the output energy from the receiver amplifier 29 may `be considered as being suppliedto lthe Y 20 terminal point 11. 'I'his output will be in the form of a voltage wave such as that shown by Fig. 67 which, it will be noted, is essentially thel same as the output signal appearing across the resistor 63 of Fig. 2, and the wave form, it will be noted, corresponds substantially to the combined wave forms of Figs. 4h and 4i.

So impressed upon the terminal 11 the several impulses must be separated from one another and from the picture portion of the signal. The synchronizing impulse is preferably maintained greater in amplitude than any other impulse or picture signal and due to this fact is selected by thetube 19 which is biased so stronglynegative that plate current is adapted to flow only during the synchronizing impulse period. The variation in the amplitude of the synchronizing signal compared to other signals has already been disclosed and set forth by the above named application of A. W. Vance. The selected impulse is 40 then amplied and reversed in polarity by means of the amplifying tube 8| which has its input circuit appropriately connected with the output from tube 19 by way of the capacity coupling 83.

It can be appreciatedr from what has been above 45 stated that the output voltage wave from the tube 8| will be of the general form shown by the curve of Fig. 6k. This signal, identified as the selected synchronizing impulse, is then impressed upon the signal delay network, generally desig- 50 nated as 85, which comprises the combination of series inductance and the shunt capacity elements 81 and 89 and aV terminating resistor |05. The delayed signal impulses, represented by the curves of Figs. 6l and 6u, due to the delay period 55 of the delay line 85 indicated by the drawings, have been delayed by the proper amount of time to coincide with the sound modulated sound impulses yet to be selected. The impulse output from the portion of the delay line 85 between the y 60 Vconnection to the output of the tube 8l and the point 9| designated by the arrows as including a delay period of .05TI arev selected at the point 9| by means of a conductor 93 connected thereto and then impressed upon the control grid of tube 65 95 by way of a capacity coupling 91 connecting therewith. 'Ihis tube 95 is normally so biased that no plate current iiows except during the time intervals during which an impulse is supplied thereto by reason of a signal being passed by the 70 delay network 85.

Also, -since the complete picture, sound and synchronizing signal is impressed upon the screen grid electrode 99 by way of the capacity connection IOI made to the terminal point 11 the plate 75 current impulse is controlled in amplitude by the odd sound modulated impulse which occurs at the same time. In this manner it may be said that the odd sound impulse signal is selected. This selection and the resulting output is represented, for example, by the curve designated as Fig. 6m.

Similarly, the further delayed vimpulse curve shown as Fig. 6u acts to control the operation of the tube |03 to select the even impulse. This tube |03 is controlled by way of the signal supplied thereto from the end of the delay line 85, which appears across the resistor |05, through a capacity coupling connection |01 connecting the end of the line with a control electrode of the tube so as to apply the signal to the control grid |09 in a manner similar to that explained in connection With tube 95. 'Ihe signal impressed upon the input terminal 11 is supplied to the screen grid electrode lll of the tube |03 by way of the capacity coupling H3 and due to the fact that' the impulse serving to change the operating characteristic of the tube |03 from a point where it is biased below cut-off to an operative position is delayed in time by a time delay period equal to .05TH later than the signal serving to control the tube 95 the even sound impulse characteristics, shown by the curve of Fig. 60, are selected.

As has already been mentioned in this discu'ssion in connection with the transmitter, the odd sound impulse should reach the sound reproducing device |39 first in the point of time of reproduction and, therefore, in the receiver system the even impulse must be delayed in time to a still further degree than has thus far been explained. Such a delay periodghas been illustrated graphically by the curve shown by Fig. 6p.

Such a further time delayof the even" impulse may be accomplished by means of a suit-- able delay line, generally designated H5, which also comprises suitable shunt capacity and series inductance elements ||1 and IIS which are connectedwith the output circuit of the tube |03 by way of a coupling condenser I2 l. This delay line H5 terminates in the usual terminating resistor |23 and has a delay period equal approximately to .5TI, which, it will be recalled, is the same time delay period as the delay network 69 shown and described in connection with Fig. 2. The signal appearing across the resistor |23 ofthe delay network H5 is then supplied through the condenser |25 by Way of a conductor |21 and a resistor |29 to a low pass filter I3| which is adapted to cut-olf at approximately '7000 cycles, that is, the assumed line scanning frequency, and above per second, although, of course, it is to be understood that this cut-off point may be varied within wide limits as desired. The output energy from the tube 95 is also supplied in common with the output of the delay line- H5 to this same low pass filter |3| by Way of the capacity coupling |33 and resistor which connects to the end of the resistor |29 leading to the lter |3|.

The combined curve resulting from the signals indicated in their general wave form by Figs. 6m and 6p has been conventionally'shown by Fig. 6r. This Wave formation contains the information for reconstructing the original sound wave shown by Fig. 6q and is obtained hy passing this wave formation through the low pass lter |3| to remove the assumed 7000 cycle scanning frequency component and all other higher frequencies. 'Ihe output voltage from the lter I3I is amplified still further, if desired, by way of an amplifier |31 and then supplied to a suitable sound reproducing device |39 connected to the output terminals Ml.

It is thus seen that as images of a subject are being reconstructed upon the image reconstructing device 31 the sound which accompanied the visual action causing the images is simultaneously reproduced by the sound reproducer |39. vIn analyzing this method of transmitting. a sound wave it may be considered, in accordance with the above explanation, that at the transmitter single point observations of the sound wave are taken at 1A400oths of a second intervals and are transmitted as such at the receiver. "I'hese values are, in effect, replotted as points of varying amplitude on a curve so as to reconstruct electrically the original wave. Obviously, the more frequently these observations are taken the more variations in the sound wave may be ascertained or, in other words, the higher frequency sound may be transmitted. This is the primary reason why itis desirable to use, where possible, more than one impulse per line of picture scanning. Any additional impulses, however, make it necessary to provide more delay networks for delaying the impulses and additional provisions to segregate the various impulses into groups because the impulse cannot be transmitted at uniform time spacing Without occurring during the picture scanning line instead of at the end of a picture scanning lineas disclosed herein. It is, therefore, apparenty that the method herein described could be used equally well for the transmission of three or more impulses'per line of picture without `departing from the spirit and scope of this disclosure. Also, it will be understood that any such additional impulses might be used for transmission of other information such as might be required for producing binaural eiects, picture background control, or sound and picture volume control. y

It should also be understood in the consideration of this invention that for convenience of illustration square-topped waves with vertical sides have been illustrated by the various curves. Such a shaped wave vis substantially impossible to transmit and would, in practice, ordinarily be replaced by impulses with rounded corners and slightly sloping sides. In practicing this invention it will be understood that the spacing between the impulses may be decreased to some extent where desired. Therefore, the present illustration must be regarded as being of a rather conventional nature and serving only to indicate and set forth the principles upon which the present invention is based rather than as deilning the invention in any concrete and limiting form.

In this connection it should be understood that wherever operating voltages have been described or illustrated, these are given merely as illustrative examples for the purpose of denning one form of the invention and that the.invention is vnot limited to any particular operating voltages or values of the various circuit constants used. all of which may be varied within wide limits.

I claim:

1. The method of transmitting simultaneously occurring audible and visual signals upon a single carrier frequency which comprises generating a transmission carrier frequency, modulating the generated carrier by visual signals for a predetermined time period, interrupting the visual signal modulation for a minute time period com'- pared to the modulating period, selecting during interruption in visual signal modulation and for a time period corresponding. to the selection period. 2. The method oi communicating sight and sound signals which comprises alternately transmitting and interrupting the transmission of sight signals, selecting during a predetermined time period during whichsight signals are transmitted minute portions of the total sound andtransmitting during sight signal interruption and for the same predetermined time interval as ineluded in selection the selected sound portions to produce at receptive points the eifect of the entire intelligence available at the transmission point.

3. Method of transmitting sight and sound signals which comprises transmitting signals representing sight for a predetermined time period, interrupting the transmission subsequent to the production of sight signals representing a single line of the subject, limiting the interruption period to the order 4of one ninth that of the transmission period, selecting during the sight transmission period a minute portion of the total sound energy available, selecting during the sight signal interruption period a second minute portion of the total sound available, and transmitting during the sight signal-interruption-period both the selected minute portions of the sound energy available during both sight transmission and interruption periods.

4. The method of communication, comprising the steps of sequentially and cyclically transmitting line image signals, synchronizing signals, and at least a pair of sound signals, conning the time period of transmission of image signals to a time order of nine times the combined synchronizing and sound transmission time period, developing at least one of the sound signals during the period of image signal transmission, and delaying the sound signal developed during the image signal transmission period for a time period at least equal to the unexpired time portion allotted to image signal transmission.

5. The method of communication which comprises the steps of transmitting visual signals, cyclically interrupting the transmission of the visual signals for a time period small compared with the time period of transmission, developing a synchronizing signal, developing a sound signal during the transmission of the visual signal, developing a, second soundsignal `during the period of interruption of the visual signal transmission, delaying the first developed sound signal, transmitting sequentially during the interruption period the developed synchronizing signal and the developed sound signals and controlling the sound transmission signals to transmit the same in the inverse order of the development of the sound signals.

6. The method of transmitting upon a single carrier frequency audible signals occurring simultaneously with a plurality of visual signals representing the light values upon successive elemental strips of a subject of which the image is desired VWhich comprises generating a transmission carrier frequency, modulating the carrier by visual signals for a predetermined time period corresponding to the time required to scan a single elemental strip of the subject, interrupting the visual signal modulation for a time period short in duration with respect to the modulating period, selecting during the visual signal modulating period a minute portion of the totalv audible signal available, delaying the selected audible signals for a time periodksubstantially one-half the visual signal transmission period, and modulating the carrier by th'e l-time delayed audible signals during periods of interruption in visual signal modulation;

'7. The method of transmitting a combined visual and audible series of signals which com-- prises producing for at least 60% of a selected unit time period a series of signals representing visual indications of successive strips of the subject, interrupting the visual signal control by the visual indications for the remaining portion of each unit time period, selecting at predetermined time .during the period of image transmission discrete portions of the total sound energy accompanying the visual indications, delaying the effects of the selected sound energy for a .time period corresponding substantially to the time equal to the difference of time of interruption of visual signals and the time of selection of the minute portion of sound energy, and transmitting during the periods of interruption of visual signals a series of independent signals representing the audible eiects originally accompanying the previously transmitted visual signals.

8. The method of transmitting sound and image signals which comprises producing and transmitting a series of signals representative of the image, interrupting the transmission of 'image signals at the end of each line of the image, selecting a minute portion of total energy representative of sound produced during the scanning of a line of the image, delaying the sound impulse and transmitting the sound impulse during the period of interruption of the image signal.

9. In a system for transmitting picture signals representations accompanied by related sound,

means for scanning a. subject of which the image is desired along a series of substantially parallel paths produced under the control of a saw-tooth formation control signal, means for transmitting during a portion of a complete cycle of the controlling saw-tooth pattern control signal other signal representations representative of the vary- V4ing lights and shadows on elemental areas of the sub'ject, means for selecting during the time of transmission of image Vsignal representations a predetermined portion of the total sound energy accompanying the picture representation, means for selecting during the periods of interruption of the transmission of picture line signals a second portion of the total available sound, means for delaying the iirst selected portion of sound representative of the subject, means for selecting s Afrom the sound signals produced in the interval between successive lines of image signals indications representativeof the desired sound, means for delaying at least Vone of the selected sound signals for a time period substantially greater than the time period during which sound signals' are received, and means Yfor reproducing the sound signals one at the natural timeof. reception and one at a delayed time of reception corresponding to the delay period to produce audible eilects representative of continuous sound production.

11. In aj system for transmitting intelligence, means for' selecting minute elements of the intelligence at substantially equal time intervals, means for delaying either the odd or even elements for a time period substantially equal to the time separating the successive elements, means for transmitting the undelayed element at the time it is selected, means for transmitting the delayed element accompanying the 'undevlayed element substantially equal to the. time yseparating the successive elements, means for Itransmitting the undelayed element at time it is selected, means for transmitting the delayed element accompanying the undelayed element continuous therewith, means for receiving the transmitted elements, means controlled in accordance with the cyclic rate of periods of transmission and reception of the selected elements for expanding the received elements in time relationship, and means for reproducing the time expanded signals to produce energy simulating the total intelligence available at the .transmission point.

12. A system for transmitting and receiving combined visual and audible signals which comprises means for transmitting and interrupting the transmission of visual signals for time periods bearing ratios of the orders of nine to one with respect to each other, means for selecting during the period of transmission and during the period of interruption of transmission of visual signals minute portions of the total sound energy available, means for delaying the signals resulting l from the selection of the sound energy occurring during the period of visual transmission-for a time corresponding substantially to the period of continuance of the visual transmission prior to its succeeding interruption, means for transmitting during the period of interruption of the visual transmission each of the selected sound signals sequentially, means for transmitting during the period of interruption of visual signal transmission a synchronizing signal to indicate the rate of repetition of the visual signal transmission, means for receiving the transmitted signals, means for reconstructing from the transmitted signals electro-optical effects synchronlzed in space position by the transmitted synchronizing impulses, means for separating the sound signals representations from the visual signal representations into independent groups of sound signall energy corresponding to the selected continuously transmitted sound signals, means for delaying one of theseparated sound signals for a time period suilcient to produce the eiect at the point of reception of two independent sound signalshaving the same time separation as the two selected signals at the point of transmission, and means controlled by the received synchronizing signal impulses for controlling the reproduction of the selected sound signal representations.

13. In a system for transmitting visual, sound and synchronizing signals over a common transmission network and wherein the picture is scanned during an elemental time period along av series of substantially parallel paths produced under the control of a saw-tooth pattern controlling electrical wave having a ratio of scanning to interruption of the order of nine to oneduring the unit scanning period for each elementalstrip of the subject, means for producing during-the longer portion of the elemental time period signals representing the varying values of iight and shadow of the several elemental areas of the subject of which the image is desired, means for producing immediately subsequent to the production of the image signals a signal indicating the rate of repetition of production of image signal effects, means for selecting during the period of production of image sign-al effects a minute portion of the total sound energy accompanying the visual effects, means for selecting during the period of interruption of transmission of visual elects a second like time duration segmental portion of the total sound energy accompanying' the visual effects, means for converting each of the selected segmental portions of sound into electrical impulses, means for delaying the impulses representative of the sound occurring during the visual transmission for a time period suilicient to cause the resulting signals to occur during the period of interruption of the visual effects and at a time period minutely separated from the selected Vsound eiects occurring during the period of interruption of visual transmission, and means for transmitting all of the selected` signals in such a relationship that the transmission is controlled by visual signals, synchronizing signals and sound signals in sequence.

14. A system for receiving and reproducing sound and visual signals in which the sound signals are transmitted between the lines of visual signals received as modulations of a received carrier frequency which comprises means for converting the visual signal portion of the received modulated carrier frequency signals into electrooptical image effects, means for producing from the sound modulated portions of the received carrier frequency energy a plurality of independent signals representative of sound accompanying the visual signals, means for delaying at least one of the independent sound signals for a time period such that the selected sound signals are substantially equally separated in time and so that one at least of the sound signals is reproduced during the time period of reproduction of visual ef-l iects, and a sound reproducing device for converting the sound signals into audible eiects to accompany the visual effects.

15. A system for transmitting combined visual and audible signals which comprises means for transmitting and interrupting the transmission of visual signals line by line bearing ratios of transmission and interruption of the order of nine to one, means for selecting during the period of transmission and during the period of interrup- -tion of transmission of visual signals minute pormeans for selecting minute elements of the intelligence at substantially equal time intervals, means for delaying either the odd or even elements for a time period, and means for continuously transmitting each group of odd and even impulses in inverted order.

AIDA V. BEDFORD. 

